1. Field of the Invention
The present invention relates to a photosensitive material drying method and apparatus which dry a photosensitive material, such as film sheet, conveyed along a conveying path.
Further, the present invention relates to a temperature controlling method and apparatus which control the temperature of a photosensitive material drying apparatus in which one surface of a photosensitive material, which has an emulsion layer formed on at least one surface thereof, is heated by heat rollers, and drying air is blown to the other surface of the photosensitive material.
Moreover, the present invention relates to a method of controlling a photosensitive material drying apparatus and to a photosensitive material drying apparatus in which a photosensitive material, which has been subject to developing processing by processing solutions, is dried.
2. Description of the Related Art
Latent images of a photosensitive material, on which images are exposed to form latent images, are processed by a photosensitive material processing apparatus such as an automatic processor. The automatic processor is equipped with a developing tank, a fixing tank and a washing tank in which developing solution, fixing solution and washing solution are stored, respectively. While the photosensitive material is automatically conveyed through each of the processing tanks in the automatic developer, the photosensitive material is successively submerged i n the developing solution, the fixing solution and the washing solution so as to undergo developing, fixing and washing processing.
The automatic processor is also equipped with a drying device. The photosensitive material, which has been processed by the aforementioned processing solutions and which has swelled due to the moisture in the processing solutions, is dried while being conveyed automatically in the drying device. In general, in the drying device, hot air is blown on the photosensitive material and the photosensitive material is dried in order to remove moisture therefrom. However, the drying air is repeatedly used in such drying devices in view of heating efficiency, and the humidity of the drying air gradually increases. Therefore, more time is required to dry the photosensitive material.
A system has been proposed in which the photosensitive material is contacted directly to a heating means and moisture is removed by drying air. The heating means of the heating device uses a heat roller or heat rollers. Namely, air containing much of the moisture evaporated from the photosensitive material heated by a direct heating means (heat rollers) is removed from a vicinity of the surface of the photosensitive material by an indirect heating means (drying air), so that the drying of the photosensitive material is expedited. Accordingly, the drying time can be shortened.
Generally, in drying processing by heat rollers, while the photosensitive material is being conveyed along an approximately straight path, the photosensitive material is held and heated between a heat roller and its counter roller at the downstream of the conveying path of the photosensitive material, and drying air is blown on the heated photosensitive material so that the evaporated moisture is removed.
However, in the above-described conventional drying process, the photosensitive material is conveyed in a direction tangent to the pairs of heat rollers. Therefore, the time during which the heat rollers contact the photosensitive material is extremely short. As a result, it is necessary for the temperature of the heat rollers to be high (approximately 100.degree. C. to 150.degree. C.) in order to effect prescribed heating in this short period of time. A drawback arises from the standpoint of safety when there is trouble and the operator is to quickly repair or work on the apparatus. Further, when the photosensitive material becomes jammed, portions of the photosensitive material in the vicinities of the heat rollers are overheated. A drawback arises in that the photosensitive material becomes wavy and can no longer be used. In particular, photosensitive materials used for printing jam easily because the base thickness of the photosensitive material is extremely thin (75.mu. to 100.mu.). It is therefore easy for drying defects such as overdrying to occur. Further, it is necessary to sufficiently guard against overheating because dimensional stability of the photosensitive materials is required.
Moreover, with regard to the adjustment of the temperature of heat rollers, the surface temperature of the heat rollers is detected, and a heater is turned on or off in response to a fall from or rise above a set temperature. The surface temperature of the heat rollers is thereby controlled to a predetermined temperature. Further, when photosensitive materials are not being dried, i.e., during a so-called "standby period", the surface temperature of the heat rollers is controlled to fall to a temperature lower than the set temperature. When a photosensitive material is to be dried, the heat rollers are heated to the set temperature from the time the photosensitive material is inserted into the drying portion to the time when the photosensitive material contacts the heat rollers. When drying is completed, the temperature of the heat rollers is lowered to the predetermined temperature of the standby state.
However, when the surface temperature of the heat rollers is raised from the standby temperature to the set temperature and drying air is blown simultaneously, if the temperature of the drying air during the time the heat rollers are heating is less than the set temperature of the heat rollers, the raising of the surface temperature of the heat rollers is disturbed. Namely, the slope of the rate of change of temperature is small.
On the other hand, when the surface temperature of the heat rollers is lowered from the set temperature to the standby temperature, if the supply of drying air, whose temperature is lower than the surface temperature of the heat rollers, is continuous, the surface temperature of the heat rollers will decrease quickly. If the next photosensitive material is sent into the drying device in a short interval, it takes time for the surface temperature of the heat rollers to return to the set temperature. If the set temperature of the drying air is even lower than the standby temperature of the heat rollers, even more time is required.
Namely, although it is ideal for the temperature raising time of the heat rollers to be fast and the lowering time to be slow, the drying air produces the opposite effect. Therefore, operational efficiency deteriorates in so far as the drying time is lengthened (the interval becomes longer), and the like.
As advances have been made in the field of electronics, image processing has become more diverse. Due to the effects of electronics on image processing, an image can be converted into an electric signal (e.g., a digital signal), various processes can be effected quickly by a computer or the like, and recording can be effected onto various recording media.
Along with the diversification of image processing, processing can be effected rapidly in the field of silver halide photography as well. The demand for rapid processing has strongly increased especially with regard to photosensitive materials such as those used for graphic arts and X-rays. As a result, various photosensitive material processing apparatuses which can rapidly process photosensitive materials have been studied and implemented. In particular, photosensitive material drying apparatuses have been studied in which a photosensitive material, which has undergone processing by processing solutions such as developing solution, fixing solution, and washing solution, is finished rapidly and with high quality.
As image processing has become more rapid, photosensitive materials, which are compatible with rapid processing, and processing solutions (such as fixing solution and the like) for processing such photosensitive materials have been developed. A trend with respect to this type of photosensitive material or to photosensitive materials processed by this type of processing solutions is to make the membrane surface of the photosensitive material more thin and suppress hardening thereof in order to achieve the requisite quality in a short time. This trend takes into account only developing and fixing processes.
However, it is known that when the photosensitive material is dried, the thickness of the membrane of the photosensitive layer and the existence of a hard membrane layer on the surface of the photosensitive layer effect the processing time. In order to shorten the drying time, the membrane surface of the photosensitive material which has been processed by processing solutions may be hardened. This suppresses the swelling of the emulsion applied to the photosensitive material so that the dryability of the photosensitive material can be improved. Namely, in order for a photosensitive material to be dried quickly, it is preferable that the membrane surface thereof be hardened, either by processing solutions (fixing solution in particular), or due to the photosensitive material itself having a hard membrane surface.
Reciprocating phenomena exist within each processing stage of rapid processing. Diversifying the combinations of types of photosensitive materials and processing solutions for processing the photosensitive materials leads to a wide range of differences in the work the photosensitive material drying apparatus must perform when a photosensitive material is dried. As a result, when photosensitive materials are subject to drying processing under the same conditions, the heat loss due to heating the photosensitive material is often large. When the heat within the drying apparatus is exhausted, it is generally discharged to the exterior of the apparatus. As the discharged heat adversely effects the operating environment of the operator in the vicinity of the photosensitive material drying apparatus, it is preferable to control this phenomenon.
Further, in order for the photosensitive material to be optimally finished by the drying apparatus, at least overheating should be avoided. Especially with photosensitive materials such as film or the like, it is also preferable that there is dimensional stability of the finished photosensitive material. For example, a film may be formed having a polyester base as a supporting body. 0n one surface thereof, an emulsion layer is applied, and on the other surface thereof, a backing layer of gelatine and dye is formed. With such a film, if the dimensions thereof at the time of exposure and the dimensions thereof after drying are the same, there is no problem if the film expands or contracts in the intermediate processes. However, when the film absorbs much moisture in the developing process and the like, drying is not effected under the appropriate conditions. The emulsion layer and the backing layer including gelatine thereby lose their ability to expand and contract, and substantially only expansion of the supporting body is observed.
When the film is dried, the respective contractions of the emulsion layer, the backing layer, and the supporting body are different. In addition, the supporting body limits the contraction of the emulsion layer and the backing layer. For these reasons, the film is often maintained in a state in which the emulsion layer and the backing layer have expanded more than the supporting body.